History and exam

Key diagnostic factors

common

diarrhea

Patients may have had diarrhea for 1 week or more at the time of presentation.[1][10]​​[27]​​​ Entamoeba histolytica diarrhea may be watery or bloody, and be clinically-indistinguishable from diarrhea caused by inflammatory bowel disease or a variety of other enteropathogens.[7]

Less than 50% of patients with a liver abscess will have diarrhea at time of presentation, although a past history of diarrhea or dysentery is common.

Other diagnostic factors

common

generalized abdominal pain

Present in most patients with amebic colitis.[7]

right upper quadrant abdominal pain

May indicate an amebic liver abscess.[1][5][7]

weight loss

About half of patients may report weight loss due to the subacute nature of the disease.[1][7]

cough

Present in up to half of patients with liver abscess.[7]​ Caused by phrenic nerve irritation and/or pleural effusion.[1]

uncommon

fever

Rare in intestinal infections but common in extraintestinal infections, such as liver and brain abscesses.[1][7]

altered mental status or limb weakness

Present with amebic brain abscess.[1][3]​​​[5]​​

dyspnea

Extension of liver abscess can cause pleural or pericardial effusion.

guarding and rebound tenderness of the abdomen

Present with acute necrotizing colitis, toxic megacolon, or peritonitis due to amebiasis.[1]

jaundice

More common with pyogenic than amebic liver abscess.[1][5]

right lung decreased air entry and percussion note

If pleural effusion is present.

Risk factors

strong

exposure in endemic areas

Most patients with amebiasis will have visited or resided in an endemic area within the previous 12 months.[1][2][4][21][22]

institutionalization (particularly of people with intellectual disability)

Outbreaks in institutions for people with intellectual disability have been reported.[2][3]​​​[4][5]​​

men who have sex with men

There is an increased prevalence of sexually transmitted amebiasis among men who have sex with men.[2][7]​​[12][19]​​​​ Commensal ameba Entamoeba dispar is responsible for most infections, but Entamoeba histolytica infections also occur in this population.[2][3]​​​​[4][5]​​​​​[12][23]

oral-anal sexual contact

Oral-anal sexual contact is a risk factor for sexual transmission of amebiasis.[3][12][19]​​​ Clustering of Entamoeba histolytica strains has been found due to oral-anal sexual contact.[18]

Those with multiple partners, including commercial sex workers, may be at increased risk.[14][18]​​

male gender

Ninety percent of amebic liver abscesses are found in men aged 20 to 40 years.[1][2][3]​​​​[4][5]​​

weak

HIV infection, past or current syphilis infection

Comorbid HIV infection and past history or positive serology of syphilis have been associated with increased prevalence of sexually transmitted amebiasis. The reasons for these associations are unclear, but may reflect similar risk factors for these infections.[11][14][15][16]​​ ​The strength of these associations may depend on the local epidemiology.

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